diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4f1e33e..e4ffbef 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -17,7 +17,7 @@ repos:
               gsw/tests/test_gibbs\.py
           )$
       args:
-        - --ignore-words-list=nin,preformed,wih,
+        - --ignore-words-list=nin,preformed,wih,pres,
 
 - repo: https://github.com/tox-dev/pyproject-fmt
   rev: v2.11.1
diff --git a/gsw/tests/test_geostrophy.py b/gsw/tests/test_geostrophy.py
index 8d69bb6..1a1508a 100644
--- a/gsw/tests/test_geostrophy.py
+++ b/gsw/tests/test_geostrophy.py
@@ -90,6 +90,21 @@ def test_dyn_height_shallower_pref():
     expected = strf0[1:] - strf0[1]
     assert_almost_equal(found, expected)
 
+def test_dyn_height_grid_bug():
+    """
+    The C toolbox had a bug in the interpolation grid generation, triggered
+    under specific circumstances demonstrated in issue #225.  The fix was copied
+    from https://github.com/TEOS-10/GSW-C/pull/87.
+    """
+    SA = np.array([34.17634373, 34.17633109, 34.17725485, 34.90704565])
+    CT = np.array([ 0.02005831,  0.02003146,  0.01868686, 1.7676452 ])
+    pres = np.array([  4.9000001 ,   5.69999981,  15.80000019, 995.90002441])
+    # Last 2 args: grid delta-p is 1; interp method is 3 (mrst).
+    dh1 = gsw._gsw_ufuncs.geo_strf_dyn_height_1(SA, CT, pres, pres[-1], 1, 3)
+    assert dh1[-1] == 0
+    dh2 = gsw.geo_strf_dyn_height(SA, CT, pres, p_ref = pres[-1], interp_method="mrst")
+    assert_array_equal(dh1, dh2)
+
 def test_pz_roundtrip():
     """
     The p_z conversion functions have Matlab-based checks that use
@@ -124,4 +139,4 @@ def test_steric_height_mrst():
     pr = cv.pr
     strf = gsw.geo_strf_steric_height(SA, CT, p, p_ref=pr, interp_method='mrst')
 
-    assert_allclose(strf, cv.geo_strf_steric_height, rtol=0, atol=cv.geo_strf_steric_height_ca)
\ No newline at end of file
+    assert_allclose(strf, cv.geo_strf_steric_height, rtol=0, atol=cv.geo_strf_steric_height_ca)
diff --git a/src/c_gsw/gsw_oceanographic_toolbox.c b/src/c_gsw/gsw_oceanographic_toolbox.c
index 36f1918..d0715e5 100644
--- a/src/c_gsw/gsw_oceanographic_toolbox.c
+++ b/src/c_gsw/gsw_oceanographic_toolbox.c
@@ -4057,7 +4057,7 @@ gsw_geo_strf_dyn_height_1(double *sa, double *ct, double *p, double p_ref,
 
     Its return argument is the number of elements used in p_i, or -1 on error.
 */
-static int refine_grid_for_dh(double *p, double p_ref, int nz,
+int refine_grid_for_dh(double *p, double p_ref, int nz,
     double dp,
     double *p_i, int ni_max,  /* size of p_i array; larger than needed */
     int *p_indices, int *p_ref_ind_ptr)
@@ -4094,10 +4094,16 @@ static int refine_grid_for_dh(double *p, double p_ref, int nz,
         /* We did not insert p_ref, so insert either p_next or p[iorig]. */
         if (p_next < p[iorig] - p_tol) {
             p_i[i] = p_next;
+            if (p_ref == p_next) {
+                *p_ref_ind_ptr = i;
+            }
             iuniform++;
         }
         else {
             p_i[i] = p[iorig];
+            if (p_ref == p[iorig]) {
+                *p_ref_ind_ptr = i;
+            }
             p_indices[iorig] = i;
             /* Skip this p_next if it is close to the point we just added. */
             if (p_next < p[iorig] + p_tol) {
diff --git a/src/c_gsw/gswteos-10.h b/src/c_gsw/gswteos-10.h
index 4fb1e76..0f27387 100644
--- a/src/c_gsw/gswteos-10.h
+++ b/src/c_gsw/gswteos-10.h
@@ -318,6 +318,8 @@ DECLSPEC extern double gsw_z_from_p(double p, double lat, double geo_strf_dyn_he
                 double sea_surface_geopotential);
 DECLSPEC extern double gsw_p_from_z(double z, double lat, double geo_strf_dyn_height,
                 double sea_surface_geopotential);
+DECLSPEC extern int refine_grid_for_dh(double *p, double p_ref, int nz,
+                double dp, double *p_i, int ni_max, int *p_indices, int *p_ref_ind_ptr);
 
 #ifdef __cplusplus
 }
diff --git a/tools/c_header_parser.py b/tools/c_header_parser.py
index b36ba88..458e1ea 100644
--- a/tools/c_header_parser.py
+++ b/tools/c_header_parser.py
@@ -59,7 +59,11 @@ def parse_signature(sig):
         argtypes.append(parts[0] + parts[1])
         argnames.append(parts[2])
 
-    retgroups = retpat.match(sig).groups()
+    try:
+        retgroups = retpat.match(sig).groups()
+    except AttributeError:
+        # For example, name doesn't start with "gsw_".
+        return None
     ret = retgroups[0] + retgroups[1]
     funcname = retgroups[2]
 
@@ -80,7 +84,8 @@ def parse_signatures(sigs):
     sigdict = {}
     for sig in sigs:
         psig = parse_signature(sig)
-        sigdict[psig['name']] = psig
+        if psig is not None:
+            sigdict[psig['name']] = psig
     return sigdict
 
 def get_sigdict(srcdir="src"):